GEE ui.panel error

I want to creata app to calculate "RMSE" index by table , but I can not select the variance in table
here is my code link: https://code.earthengine.google.com/?scriptPath=users%2Fdusgh1090870%2Fapps%3Atest1

Map.setCenter(120,30,5)
//Welcome menu
var AovpPanel = ui.Panel({
  style:{
  position:'top-center'
  }
});
var AovpPanel1 = ui.Panel({
  style:{
  position:'bottom-left'
  }
});
var AovpTitle=ui.Label({
      value: 'Analysis on vectorization precision V1',
      style: {
        margin: '1px 10px 1px 10px',
        fontSize: '20px',
        fontWeight: 'bold'
        }
    });
var AovpSubtitle=ui.Label({value:'Written by wu pengcheng, Tibet University',
      style: {
        margin: '1px 10px 1px 10px',
        textAlign: 'center',
        fontSize: '10px'
        }});
var AovpSubtitle1=ui.Label({value:'Email: [email protected] ',
      style: {
        margin: '1px 10px 1px 10px',
        textAlign: 'center',
        fontSize: '10px'
        }});
var data;
var Aovpinputdata=ui.Textbox({
      placeholder: 'Input your data url',
      onChange:function(text){
      data = Aovpinputdata.getValue();  
      }
    });
var Aovpreaddata=ui.Button('read data');
Aovpreaddata.onClick(function(){
var table = ee.FeatureCollection(data);
print(table)
});
var table = ee.FeatureCollection('data');
var table = table.select(['AWEInsh',"EWI"]);
var Aovpsetvar = ui.Select({
  items:Object.keys(table),
  onChange:function(key){
  table = table["AWEInsh"];
  }
});

AovpPanel.add(AovpTitle);
AovpPanel.add(AovpSubtitle);
AovpPanel.add(AovpSubtitle1);
AovpPanel.add(Aovpinputdata);
AovpPanel.add(Aovpreaddata);
AovpPanel.add(Aovpsetvar);


Map.add(AovpPanel);
Map.add(AovpPanel1);